Pressure regulators are generally known in the art for reducing a high input pressure to a lower (regulated) output operating pressure. Many pressure regulators operate by limiting the size of the fluid flow path through which the input pressure is allowed to flow in order to decrease the pressure to a suitable output pressure. Generally, the pressure regulator is provided with a flexible diaphragm that is biased using a spring to press a valve member against a valve seat. The force of the spring is often adjusted so the valve opens at a predetermined pressure, resulting in a set outlet pressure. However, if there are large fluctuations in the inlet pressure, the spring must be continuously adjusted to maintain the desired outlet pressure.
One problem generally encountered in pressure regulators is internal leakage of the valve also known as “regulator creep.” Regulator creep often occurs due to a faulty valve to valve-seat seal resulting in a small, undesired amount of fluid leaking through the valve. While this small leakage may not cause concern in certain applications, some situations have a limited amount of fluid that can be supplied to the inlet and thus even small losses can have serious consequences. Such an example is in a portable infusion device that has a pressurized bladder. If the pressure in the bladder leaks over time, the infusion device may need to be replaced prematurely. Internal leakage can also occur if the connection between the valve stem and the diaphragm loosens. Typically, the valve stem is held relatively loosely to the diaphragm, if at all. Generally, this is not seen as a problem because the valve stem is typically compressed against the diaphragm by the fluid rather than pulled away from it. However, in some situations, this may not be the case and the pressurized fluid acting on the diaphragm may attempt to pull the valve stem away from the diaphragm. Currently there is no acceptable system for efficiently retaining the valve stem to the diaphragm.
Another problem with many pressure regulators that utilize a diaphragm is the excessive number of parts. Typically, the diaphragm is clamped into position in the regulator body using some sort of a retaining ring or an additional seal. The majority of diaphragms are produced as a sub-assembly consisting of up to three components, the diaphragm being sandwiched between a diaphragm rivet and spring rest. This itself can also be a potential leak path. Alternatively, the diaphragm may be held in place by clamping the diaphragm between the regulator body and a cap. One problem with this design is that if the cap becomes loosened due to vibrations, for example, the diaphragm could become unsealed resulting in a leaking regulator. Another problem with this design is that it requires an additional component to adjust the compression of the spring. Neither situation is ideal.
One particular application that has recently started to implement pressure regulators is in portable infusion devices. The infusion device includes a pressure source, typically around 2.5 bar (36.3 psi); however, the pressure may vary from one application to another. The pressure regulator is used to decrease the pressure to around 0.5 bar (7.3 psi), which is then delivered to a bladder at a constant pressure. The constant pressure delivered by the pressure regulator acts via the bladder to compress the infusion bag to deliver a constant flow of fluid to a patient. As can be appreciated, any variation in the pressure delivered from the pressure regulator could have serious consequences. Therefore, even small leaks in the system can be disastrous. In addition, because the infusion devices are typically designed to be disposable, the pressure regulator used with the system should be relatively inexpensive to manufacture.
The present invention provides a pressure regulator with an increased sealing potential, which reduces the risk of the regulator leaking. Furthermore, the pressure regulator of the present invention has reduced the number of necessary parts, thereby decreasing the cost of manufacturing. Therefore, the pressure regulator of the present invention may comprise a disposable unit.